The present invention relates to a fuel injector.
A previously proposed fuel injector is described in German Published Patent Application No. 196 265 76. This fuel injector has a valve closing body that works together with a valve seat face designed on a valve seat carrier to form a seal seat. The valve closing body can be operated electromagnetically by a solenoid with a valve needle extending in the interior of the valve seat carrier and an armature connected to the valve needle on the end opposite the valve closing body. The valve seat carrier is inserted into a housing body and can be prestressed by a threaded ring which is screwed into the housing body against a stroke adjusting disk inserted between the housing body and the valve seat carrier. The stroke adjusting disk is thus located inside the housing body. The function of the stroke adjusting disk is to adjust the stroke of the valve closing body in electromagnetic operation of the fuel injector. A variation in thickness of the stroke adjusting disk thus leads to a variation in axial position of the valve seat face. The valve stroke is thus set for a certain length of the valve needle and a certain position of a stop face for the armature.
Before assembly of the fuel injector, various dimensions of the individual parts of the fuel injector that have an influence on the valve stroke are measured, and a suitable stroke adjusting disk is paired with it in such a way as to yield valve strokes in a very narrow tolerance range regardless of the manufacturing tolerance.
A disadvantage of the fuel injector described above is that the stroke adjusting disk has a relatively small diameter, and therefore there is not sufficient protection against tilting of the valve seat carrier in all applications. It is a particular disadvantage that the stroke adjusting disk is not located inside the housing body, and therefore, joining the housing body, the valve seat carrier and the stroke adjusting disk requires the stroke adjusting disk to be inserted into the interior of the housing body, which is complicated in terms of the manufacturing technology. Furthermore, there is the risk of soiling of the thread needed for the threaded ring.
A known fuel injector having a similar design is illustrated in FIG. 1 and is described in greater detail below. This design corresponds to that in Germans Published Patent Application No. 196 26 576 with regard to the arrangement of the stroke adjusting disk, except that the valve seat carrier is connected to the valve housing by a flange connection rather than by a threaded ring. This fuel injector also has the disadvantages described above.
The fuel injector according to the present invention however, has the advantage that the stroke adjusting disk can be installed easily and inexpensively because it is arranged on the exterior periphery with respect to the housing body. At the same time, this yields the advantage that the valve seat carrier is secured better against tilting with respect to the housing body by the stroke adjusting disk because of the relatively large diameter of the stroke adjusting disk.
Furthermore, it is advantageous that assembly of the stroke adjusting disk is not susceptible to soiling, and the number of individual parts is reduced due to the elimination of the threaded ring which is provided in the related art.
The stroke adjusting disk can preferably be inserted into a peripheral groove of the housing body and is in contact with the housing body on an inlet-side end face and with a peripheral projection of the valve seat body on a spray-side end face. The connection between the housing body and the stroke adjusting disk on the one hand and between the stroke adjusting disk and the valve seat carrier on the other hand can be accomplished by a weld. The stroke adjusting disk not only has the function of defining the axial position of the valve seat carrier with respect to the housing body and thus defining the valve stroke, but also at the same time has the function of a connecting element between the housing body and the valve seat carrier. The welds preferably cause a weld contraction strain which prestresses the housing body, the stroke adjusting disk and the valve closing body relative to one another. This yields an especially great strength.
Preferably an inlet end of valve seat body can be inserted into a spray end of the housing body, and these parts can be sealed with respect to one another by a seal. This has the advantage that the pressure of the fuel in the fuel injector does not advance as far as the stroke adjusting disk and the welds and thus there is no load on the welds due to the fuel pressure. The connection between the housing and the valve seat carrier as well as the stroke setting are therefore largely independent of the fuel pressure.
It is advantageous that the welds can be produced easily by welding tools applied externally and radially.